Regulated power supply



April 24, 1962 D. s. COLBURN 3,031,578

REGULA'I'ED POWER SUPPLY Filed Oct. 29, 1959 INVENTOR. DAVID S. COLBURNATTORNEYS down voltage of the Zener diode.

Zener diode however is that the constant voltage which United StatesPatent 3,031,578 REGULATED POWER SUPPLY David S. Colburn, Palo Alto,Calif assignor to Beekman Instruments, Inc., a corporation of CaliforniaFiled Oct. 29, 1959, Ser. No. 849,561 8 Claims. (Cl. 250-205) Thisinvention relates generally to a regulated power supply and moreparticularly to a regulated power supply for use with apparatusrequiring both a high and a low regulated voltage.

In many applications, it is desirable to have a source of relativelyconstant low voltage high current power and at the same time a regulatedhigh voltage low current power. For example, in colorimetry it isdesirable to provide a constant low voltage high current power to thelight source. It is equally desirable to provide high voltage lowcurrent power either to a vacuum tube voltmeter or to an amplifierserving to amplify the output of a photoelectric cell. Additionally, alow voltage high current regulated supply may be desirable to providerelatively constant current to either of the associated tubes inelectrical equipment.

It is a general object of the present invention to provide an improvedregulated power supply having a low voltage high current output and ahigh voltage low current output.

It is a general object of this invention to provide an improvedregulated low voltage high current power supply.

It is a further object of this invention to provide a power supplyhaving the above characteristics employing a voltage regulator tube anda Zener diode complementing each other.

These and other objects of the invention will become more clearlyapparent upon reading the following description in conjunction with theaccompanying drawing in which the single FIGURE is a schematic diagramof one embodiment of the invention.

Referring to the drawing: The power supply includes a transformer 11having a primary winding 13 and secondary windings 15 and 17. Thewinding 15 is connected to a half wave rectifier circuit including thediode 19, filter capacitor 21, and resistor 23. The rectifier circuitprovides a source of unregulated D.-C. voltage to a voltage regulatingdevice which may be the voltage'regulator tube 25. The electrodes of thevoltage regulating tube 25 are connected to the terminals 27 and 29 bythe lines 31 and 33, respectively.

A voltage divider network 34 including resistors 35, 37 and 39, and aZener diode 41 is connected between the terminals 27 and 29. Theproperties of the Zener diode 41 are such that when connected in serieswith an external resistance across a voltage supply, a relativelyconstant voltage is maintained across the diode regardless of thevariations at the voltage terminals provided that the voltage in theterminals exceeds a minimum break- Characteristic of the is maintainedmay bemade variable by variations in current. through the diode.Consequently it is desirable in the use of Zener diodes to provide arelatively constant current source.

In the circuit shown, a relatively constant current is maintainedthrough the diode 41 by the use of the regulator tube 25 in conjunctionwith the resistors 35, 37 and 39. .Since the voltage at the terminals 27and 29 is relatively constant the current through the voltage dividernetwork will likewise be constant. Consequently the voltage across theZener diode 41 is maintained at a substantially constant value.

The secondary winding 17 is connected to a full wave 3,031,578 PatentedApr. 24, 1962 rectifier circuit including the diodes 43 and 45 and thefilter capacitor 47. The full wave rectifier serves as supply voltagefor the regulating and amplifying transistors to be described presently.One side of the full wave rectifier circuit is connected directly to theoutput terminal 49 of the low voltage regulated supply through the line51. The other side of the full wave rectifier circuit is connected tothe low voltage regulated output terminal 53 through the line 55 and avariable impedance device such as transistor 57. A low voltage highcurrent supply is provided therefore at the terminals 49 and 53.Regulation of the low voltage supply is directly provided by the use ofthe transistor 57.

The base of the transistor 57 is connected to the emitter of thetransistor 59. The emitter of the transistor 59 is connected to line 51through the resistor 61 while the collector of the transistor 59 isconnected to the line 55. The transistor 57, therefore, operates as anemitter follower of the transistor 59. The base of the transistor 59 isconnected to the terminal 27 through resistors 63 and 35.

A transistor 65 has its collector connected to the base of thetransistor 59 and its emitter connected to the line 51 through theresistor 67. The base of the transistor 65 is connected to a voltagedivider network 68 including the resistors 69 and 71 connected in seriesacross the terminals 53 and 49. The collector of transistor 73 isconnected directly to the terminal 53. The base of the transistor 73 isconnected to one side of the Zener diode 41 while the emitter of thetransistor 73 is connected to the other side of the Zener diode throughthe resistor 67 and the line 51. A capacitor 74 is connected between theline 51 and the base of transistor 59 to prevent oscil1ation due tofeedback.

In operation, a source of A.-C. potential is applied to the primarywinding 13 thereby producing a regulated high voltage at the terminals27 and 29. Current will flow through the transistor 57, dependent uponthe voltage from the full wave rectifier and the resistance at theterminals 49 and 53 and the base current applied to the transistor 57.The collector current of transistor 57 will also be dependent upon thecollector current of transistor 73.

The Zener diode 41 in conjunction with the resistor 67 and thetransistor 73 act as a reference to the voltage regulator. The voltageacross the diode 41 is applied between the base of transistor 73 and theline 51 to establish the reference voltage.

The transistor 65 has its emitter connected to this reference voltageand its base connected to a fraction of the output voltage determined bythe resistors 69 and 71. Transistor 65 serves to amplify any voltagedifference between the reference voltage and this fraction of the outputvoltage. The amplified difference voltage is applied to the base oftransistor 59 which, in turn, controls the series regulating transistor57.

Assuming an increase in the line voltage at the winding 13, emittercurrent of the transistors 57 and 59 will tend to increase causing agreater voltage at the terminals 49 and 53. The greater voltage at theterminals 49 and 53, however, causes an increase of base bias at thetransistor 65. Consequently, the current flow throughthe transistor willincrease thereby deflecting part of the base current from the transistor59. With the decreased base current at transistor 59, its emittercurrent necessarily decreases, thereby causing the consequent decreaseof the emitter current of the transistor 57 and of the voltage atterminals 49 and 53.

In use of the circuit described with a colorimeter', the high voltageterminals 27 and 29 may be connected across a vacuum tube amplifier suchas tube 75, thereby to establish a constant cathode to plate amplifiervoltage. To

further limit variations and amplification of the amplifying tube 75,the heater of the tube may be connected to the low voltage terminals 49and 53. With uch a connection, the amplification factor of the tube 75is extremely constant. By connecting a light source 77 across the lowvoltage terminals 49 and 53, an extremely constant value light energycan be obtained. Consequently, when the light from the source 77 ispassed through a sample 79 onto a photocell 81, exact measurements maybe obtained as to the amount of source reaching the cell 81 andconsequently accurate determination of a sample 79 can be accomplished.

By using the regulated voltage divider network 34 having voltage levelsmore negative than the consequent output (at terminal 53), a continuoussource of collector current is provided for the transistor 65. Thesource is regulated thereby assuring a constant operation level for thetransistor 65.

Apparatus in accordance with the foregoing was constructed. The variouscomponents shown in the diagram were as follows.

Transistors:

Tubes 75 /2 12AU7. Photocell 81-; CE34. Transformer:

Primary 110/220 volts.

Secondary 15-30 volt center tapped; 550 milliamperes. 17-110 volt, 15milliamperes.

Rectifiers:

19 Sarkes Tarzian 40K.

43 Sarkes Tarzian 10K.

45 Sarkes Tarzian 10K. Capacitors:

21 12 mt. 250 volts.

47 500 mi. 25 volts.

74 .02 mf. 100 volts. Zener diode 41 1N429 Resistors (ohms):

80 100 meg.

Thus, it is seen that there is provided a combination high voltageregulating device employing element such as an inexpensive voltageregulating tube acting as a constant current source for a Zener diodeand a constant plate voltage source for an amplifier tube. The Zenerdiode acts as a reference for low voltage supply terminals whichprovides a constant voltage for the heater of the amplifier tube and asa constant low voltage load source.

I claim:

1. A power supply for providing a high and a low voltage outputcomprising a source of regulated high voltage being connected to a pairof high voltage output terminals,

a first voltage divider across said high voltage output terminalsincluding a Zener diode and a resistor, a source of low D.-C. voltage, aplurality of variable current devices each having two current carryingelectrodes and a control electrode, said source of low voltage and firstof said variable current devices being series connected to a pair of lowvoltage output terminals, second of said variable current devices and aresistor being series connected across said source of low voltage toprovide a current path through said resistor, the junction of saidresistor with said second variable current device being coupled to thecontrol electrode of said first variable current de- Vice, said secondvariable current device being connected to a source of conducting biason said first voltage divider, a third of said variable current deviceshaving its current carrying electrodes connected across said source ofbias, a second voltage divider being across said low voltage outputterminals and having one side connected to control said third variablecurrent device, and a fourth of said variable current devices having onecurrent carrying electrode connected to a current carrying electrode ofsaid third variable current device and having each current carryingelectrode connected to one of said low voltage output terminals, saidfourth variable current device being connected to said Zener diode toprovide a regulated source of conducting bias.

2. A power supply as defined in claim 1 wherein said variable currentdevices are transistors.

3. A power supply comprising a high voltage and a low voltage regulatingdevice, each adapted to be connected to a source of D.-C. voltage, saidhigh voltage regulating device being connected to control currentthrough the low voltage regulating device, said low voltage regulatingdevice being connected to provide a low voltage reference and means forconnecting a load across said voltage reference.

4. A power supply in accordance with claim 3 wherein said low voltagereference device is a Zener diode.

5. A power supply as defined in claim 3 together with means to connectan additional load across said high voltage regulating device.

6. In a colorimeter including a light source, a photocell and aphotocell voltage amplifying tube, said amplifying tube having an anode,a cathode, and a grid electrode; a power supply comprising a source ofregulated high voltage connected across said anode and said cathode,said photocell being connected to said grid electrode, a voltage dividerincluding a Zener diode and at least one resistor connected across saidregulated high voltage, a source of low D.-C. voltage providing anoutput voltage, a variable current device connected in series betweensaid output voltage and the source of low voltage, and a voltagereference controlled by voltage across said Zener diode connected tosaid output voltage, said output voltage connected to supply regulatedlow voltage to said light source.

7. A power supply as defined in claim 6 together with a second variablecurrent device having one current carrying terminal connected to oneside of said voltage reference and another current carrying terminalconnected to a point on said voltage divider whereby continuous currentis produced by said second variable current device.

8. A power supply as defined in claim 6 wherein said amplifying tubeincludes a heater, said heater being connected to said output voltage toprovide a regulated heater voltage.

References Cited in the file of this patent UNITED STATES PATENTS2,762,963 Lucks et al Sept. 11, 1956 2,896,151 Zelinka July 21, 19592,915,693 Harrison Dec. 1, 1959

